Alpha-Gal Syndrome: A Review for the General Internist

Alpha-gal syndrome develops in some individuals who have had tick bites which result in IgE responses to alpha-gal, a carbohydrate not found in humans. Patients with alpha-gal syndrome develop symptoms when they ingest mammalian meat, which contains this oligosaccharide. Often the response to this exposure is delayed and occurs 2 to 6 h post-ingestion. Symptoms can include skin rashes, urticaria, gastrointestinal symptoms, and occasionally anaphylaxis. In some patients, the initial site of the skin reaction is at the location of the prior tick bite. The frequency of the syndrome is uncertain but the geographic distribution is predominantly in areas with the lone star tick. The diagnosis depends on careful attention to the time interval between the ingestion of meat and the development of the symptoms. In addition, a history of prior tick bites is important for considering this diagnosis. Diagnostic studies include skin tests, serologic tests for specific IgE, and food challenges, with varying risks for anaphylaxis. The treatment of patients with acute presentations frequently includes intramuscular epinephrine, oral antihistamines, and corticosteroids. Long-term management involves diet modification with the elimination of meat. Patients can also have adverse reactions to medications, such as set cetuximab, heparin, monoclonal antibodies, and pancreatic enzymes, and clinicians will likely have difficulty identifying these reactions. If patients have a good response to diet modification and have a significant reduction in their specific IgE level to alpha-gal, they potentially can resume eating meat in their diet. This should be done under the direction of a specialist.